Calculate the gradient of a curve x^3+y^3-2xy=11at the point A (2,1)if r=2i+3j and 9=8i+7j.evaluate r.q and/r+q/

r•q = (2i+3j)•(8i+7j) = 2*8 + 3*7 = 16+21 = 37

r+q = 10i+10j, so |r+q| = 10√2

x^3 + y^3 - 2xy = 11
3x^2 + 3y^2 y' = -2y -2xy'
y' = (3x^2 - 2y)/(2x - 3y^2)
so y' at (2,1) = (3*4 - 2*1)/(2*2 - 3*1) = 10